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Biomedical subjects

E R Davies

Publications and source records attributed to E R Davies.

At least 19 recordsLinked to original sources
PubMed1992

Fat-suppression magnetic resonance imaging in the preoperative localization of parathyroid adenomas.

Prospective localization of parathyroid adenomas was attempted in 16 patients with hyperparathyroidism prior to surgery. All patients had magnetic resonance imaging (MRI) using T1-weighted spin-echo (SE) sequences and a fat-suppression sequence, the short-tau inversion recovery (STIR) sequence. Correlation with the results of surgery yielded an overall sensitivity of 71% and a specificity of 94%. Performance was good in patients with previous surgery and with ectopic tumours. We believe that fat-suppression MRI is a valuable technique in the preoperative localization of parathyroid adenomas in patients with hyperparathyroidism.

Adenoma↗
PubMed1991

Failure of peripheral arterial balloon angioplasty: does platelet deposition play a role?

The pathophysiological response to peripheral percutaneous transluminal balloon angioplasty in 20 patients was investigated using 111-Indium labelled platelets. Platelet deposition was quantified by measuring the degree of radioactivity uptake at angioplasty and control sites using a computer linked system and expressing the uptake as a ratio of angioplasty/control. Following platelet labelling, scans were performed before angioplasty and at 1, 24 and 48 h after angioplasty. To assess patency of the angioplasty, ankle brachial Doppler pressure indices were performed and supported by repeat angiograms if doubt of patency existed. All patients were followed-up at 1 week, 1 month and 6 months to correlate the degree of early platelet uptake with failure. The mean +/- sem platelet radioactivity ratio at the angioplasty site increased from 1.1 +/- 0.1 prior to the procedure to a peak of 2.1 +/- 0.3 at 1 h (p less than 0.01), 1.6 +/- 0.2 at 24 h (p less than 0.05), and 1.7 +/- 0.3 at 48 h (p less than 0.05). Angioplasties that failed within 6 months tended to have a higher maximum early platelet uptake (3.1 +/- 0.6) compared to successful angioplasties (1.9 +/- 0.3) but the difference was not significant in the numbers studied. This study provides a suitable model to assess the role of platelet accumulation in angioplasty failure and the influence of various antiplatelet regimes.

Adult↗
PubMed1991

Optical attenuation characteristics of breast tissues at visible and near-infrared wavelengths.

Optical experiments are described for measuring the attenuation characteristics of breast tissues at visible and near-infrared wavelengths. Total attenuation coefficients post mortem were measured directly in thin tissue sections. They are usually within the range from 10 to 30 mm-1, are rather higher in fat than in fibroglandular specimens and decrease with increasing wavelength. The scattering phase function is strongly forward-peaked with the mean cosine of scattering in the range from 0.85 to 0.97 and appearing more forward-peaked in fat than in fibroglandular tissue. The reduced scattering coefficient is of the order of 1 mm-1 in all tissues. Absorption coefficients were measured indirectly in optically thick sections. They are typically between 0.1 and 0.5 mm-1 at wavelengths around 580 nm and an order of magnitude lower at 850 nm. At 580 nm and shorter wavelengths the absorption in carcinoma is significantly higher than in adjacent uninvolved tissue. Significant differences were observed in the first-order derivatives of the transmission spectra of carcinoma and surrounding tissues at certain infrared wavelengths. Transmission spectra measured in vivo across the wavelength range from 500 to 860 nm have a similar form to the spectra of excised samples. Linear absorption coefficients are generally of the same order of magnitude as those found in vitro although they are lower at green wavelengths.

Adenocarcinoma, Scirrhous↗
PubMed1991

Monte Carlo modelling of light propagation in breast tissue.

Light transport in three-dimensional plane-parallel tissue slabs has been modelled by Monte Carlo analogue simulation. The model design has allowed the study of transmission properties that are pertinent to imaging systems for the detection of breast cancer. An important aspect of the investigations is that they make use of data obtained from quantitative measurements of light scattering and absorption in normal and pathological breast tissues. It is shown that an imaging technique which used a raster scanning laser and detector arrangement and plane-parallel compression of the breast could have considerable advantages in terms of improved transmittance, spatial unsharpness and contrast. Time-of-flight gating of images is also found to be beneficial provided that the light intensities after temporal filtering remain adequate.

Breast↗
PubMed1977

99Tcm-Sn pyrophosphate scanning in suspected acute myocardial infarction using a mobile rectilinear scanner.

99Tcm stannous pyrophosphate injected intravenously gives a positive image of freshly damaged myocardium but not of normal or scarred myocardium. It is safe, cheap and generally available. One hundred and forty patients admitted to hospital with possible myocardial infarction were scanned with a mobile rectilinear scanner of the type available in most district general hospitals. When the diagnosis of infarction was definite on clinical, electrocardiographic and enzyme criteria the anterior scan was positive in 31 out of 36 patients (86%); and when it was probable, the scan was positive in 28 out of 41 (68%) and when it was doubtful the scan was positive in 23 out of 63 (37%). The optimum time for scanning was between the second and seventh days. Pyrophosphate scanning is a very valuable investigation even though it is not an absolute discriminator of myocardial infarction. It is useful in assessing patients with atypical or doubtful symptoms of infarction where the ECG is already abnormal or where there are other causes of raised enzyme concentrations. False negative scans are not common, but a negative scan does not outweigh strong alternative evidence of infarction. Positive scans occur in some patients with unstable angina without confirmatory evidence of infarction. Positive scans due to extracardiac lesions are distinguished readily.

Humans↗
PubMed1977

Renography as a prognostic index of urinary tract problems in childhood.

Many radiological methods are used in investigating urinary tract problems in children, and some are poorly tolerated. The simplest and most acceptable technique is isotope renography. Its value has been assessed in predicting the outcome of urinary tract problems in 91 children over the age of 2 years presenting consecutively over a period of 3 months. The results of initial assessment by renography and radiography have been compared with the final clinical assessment 7 years later. 35 patients were identified as being "at risk" and all of these had abnormal renograms and radiograms. Normal renographys was found unexpectedly in some patients with severe reflux but with a good final result. It is concluded that renography can be used to screen children with urinary tract infection, thereby excluding the less acceptable radiological investigations unless the renogram is abnormal.

Child, Preschool↗
PubMed1977

The value of urography following lymphography in malignant diseases.

The need for urography following ascending pedal lymphography in malignant disease has been studied in 298 consecutive patients. Forty per cent of the urograms were abnormal. Urographic abnormalities due to the disease being investigated were heralded by abnormal lymphography except in four patients, three with carcinoma of the bladder and one with carcinoma of the cervix. The majority of abnormalities unrelated to the disease being investigated were of no significance. In a small number there was congenital malposition of the kidney so that it fell within the proposed field of treatment. It is concluded that it is unnecessary to do routine urography with every lymphogram. Indications for urography are abnormality or suspected abnormality of the lymphogram, failure to locate the kidneys on plain films and clinical indications such as carcinoma of the bladder or carcinoma of the cervix.

Adolescent↗
PubMed1976

131I Rose Bengal scanning and clearance ratios in the investigation of jaundiced patients.

It may be difficult to distinguish between obstructive and non-obstructive jaundice despite the use of clinical, biochemical and radiographic tests. Endoscopic cannulation tests promise to be the most accurate means of separating the two groups, but they are not yet widely available, and are not entirely safe. In contrast, the 131I-Rose Bengal test is simple, safe and comparatively widely available. Its accuracy in 70 jaundiced patients is reviewed to determine whether it still has a place in the investigation of jaundiced patients. Blood clearance traces, intestinal radioactivity traces and serial abdominal scans were done during a period of 3 h. The blood clearance ratios were not helpful discriminators, and the most helpful information was the timing of intestinal radioactivity. Its rapid appearance excluded mechanical obstruction. A delay of up to 3 h in its appearance was characteristic of cholestasis. A delay of more than 3 h was found in all cases of mechanical obstruction, but also in ten cases of severe cholestasis which could not be distinguished from those with mechanical obstruction. A follow-up examination within another ten days was of diagnostic value in two of these cases and the overall accuracy of the test was 86%. The potential value of prolonging the test to 24 h is discussed. It is concluded that the 131I-Rose Bengal test is a helpful diagnostic discriminator in the great majority of patients with jaundice. It is offered as a screening procedure for specialised techniques.

Biliary Tract Diseases↗
PubMed1975

Gall-bladder emptying measured by a radioisotopic method.

A method of oral radioisotope cholecystography is described using 131I sodium ipodate. Gall-bladder emptying was measured by this method and radiographically: (a) in a model, (b) in 34 patients having oral cholecystography. There was a good correlation between the two methods of measuring volume changes, both in vitro and in vivo. The isotope cholecystogram has the advantage of a lower radiation hazard, and is the only satisfactory method of studying the onset, rate and duration of gall-bladder emptying. These may be easily measurable markers of disorders of the upper small bowel.

Cholecystography↗